How do we recognize and use fossils in outcrop?

Hilary Lackey
Cal Poly - Pomona; Cal State San Bernardino
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Students find fossil hunting rewarding and fun. However, it is important that field trips to fossil localities go beyond mere hunting ("Is this a fossil?") and lead students to ask "What is the significance of this fossil?" This activity is intended to get students thinking like paleontologists as soon as they hit the outcrop. Preservation, taxonomic identification, and using fossils in geologic interpretation are addressed.

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This activity is intended for introductory geology students, with no prior lessons on fossils, going on a field trip to a fossiliferous locality. Alternately, it can be used as a refresher for intermediate paleontology or historical geology students before a field trip. It has multiple sections that could be spread over two class or lab periods.

Skills and concepts that students must have mastered

This project assumes little to no prior experience with fossils or field work.

How the activity is situated in the course

A stand-alone exercise.


Content/concepts goals for this activity

Content/concept: taphonomy, taxonomic identification, ecological interpretation

Higher order thinking skills goals for this activity

Higher order: formulating hypotheses, field observation, scientific writing

Other skills goals for this activity

Description of the activity/assignment

Getting students to "put on paleontologists' hats" before their first fossil-hunting field trip allows for a more enriching field experience. Rather than handing out an instructor-prepared field guide (that few students read, anyway), the students essentially work up their own geologic/paleontologic interpretation of a site, using a custom toolkit they develop through classroom and homework exercises.
The activity begins with a worksheet that can be completed in groups during class (recommended) or as homework. Students are asked to imagine scenarios of fossil preservation, suggest factors that influence the completeness of the fossil record, and think of ways that fossil assemblages can give clues to the stratigraphic position and paleoenvironment of a rock formation. The instructor is involved as a guide, introducing concepts and terminology as needed. Students will also discuss – with help from a textbook, specimens, or slide presentation - how the characteristics of major fossil groups might be used to identify a fossil in outcrop (for example, the coil of a gastropod, the pinnules of a crinoid).
Next, each student is assigned to be an expert on one taxon or faunal group that they will encounter on the trip. This requires reading a fossil identification guide or instructor-prepared handout. They will make an "expert's notecard" to bring along on the field trip, and will be expected to find and present examples of their fossil(s) on the field trip. The taxonomic level or groups assigned will vary depending on the fossil assemblage and the class size.
The activity culminates with the field experience, during which students keep a detailed field notebook (bringing along their in-class worksheets for reference). In the field, students will identify modes of preservation, assist one another as "experts" in fossil identification, and discuss the paleoecological and paleoenvironmental setting of the geologic section. After the field trip, the class compiles a faunal list for the site. Each student writes up an interpretation based on their individual observations and those made as a class.
This set of activities can be streamlined if, for instance, the field trip is only a small unit of a general geology course. Rather than using open-ended discussion questions on the preliminary worksheet, the instructor can assign reading or give a lecture that covers modes of preservation and other concepts that students will use to complete the worksheet. The goal remains, however, for students to think about what they will observe at the outcrop BEFORE they are on the rocks.

Determining whether students have met the goals

Students will turn in detailed field notes, a one-page interpretation of the site, along with the pre-trip worksheet and "expert's notecard."

More information about assessment tools and techniques.

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